# Letta vs Zep: open-source agent memory vs production memory layer in 2026

**Source:** https://promtable.com/compare/letta-vs-zep

> Letta (formerly MemGPT) is the OSS virtual-context agent framework. Zep is the production memory layer with temporal facts + Graphiti knowledge graph. Pick Letta for OSS + virtual context, Zep for production.

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Letta (formerly MemGPT) is the OSS virtual-context agent framework. Zep is the production memory layer with temporal facts + Graphiti knowledge graph. Pick Letta for OSS + virtual context, Zep for production.

## At a glance

| Dimension | Letta (MemGPT) | Zep |
|---|---|---|
| Form factor | OSS framework | Hosted + OSS service |
| Memory architecture | Virtual context (main + archival) | **Temporal facts + Graphiti knowledge graph** ✓ |
| Knowledge graph | No | **First class (Graphiti)** ✓ |
| Production maturity | Growing OSS adoption | **Production-grade hosted + OSS** ✓ |
| API ergonomics | Python-first | **REST + Python + TS SDKs** ✓ |
| Setup complexity | Self-host required | **Hosted or self-host** ✓ |
| Cost | **Free OSS + compute** ✓ | Per-seat + per-op |
| Best for | Research + OSS exploration | Production agent memory |

## Verdict

Letta is the right pick for research, OSS-preferring stacks, and teams exploring the virtual-context memory pattern Letta pioneered. Zep is the right pick for production agent memory — temporal facts, knowledge graph via Graphiti, and ergonomic SDKs make it the production default in 2026. For OSS / research, Letta. For shipping agent memory in production, Zep.

## When to pick which

- **Letta (MemGPT)** — OSS / research, virtual-context exploration.
- **Zep** — Production agent memory, temporal facts, knowledge graph.

## FAQ

### Letta or Zep for production?

Zep — production memory layer with stronger ergonomics in 2026.

### Best free agent memory?

Letta (OSS) or Mem0 (OSS + cloud).

### Best for knowledge graph memory?

Zep — Graphiti is first class.

## Related

- [/compare/mem-vs-zep](https://promtable.com/compare/mem-vs-zep)
- [/alternatives/zep](https://promtable.com/alternatives/zep)
- [/alternatives/letta](https://promtable.com/alternatives/letta)

*Last updated: 2026-06-01*
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